Secondary hypothyroidism in adults: diagnosis and treatment

Abstract

Secondary hypothyroidism is a rare disease. There is a number of questions and difficulties in diagnosis and management of this condition. There are two forms of secondary hypothyroidism: congenital (casuistic seldom) and acquired. The main causes of secondary hypothyroidism in adults are tumors of the hypothalamic-pituitary region and the state after surgical and radiation effects on this area. Hormonally active and inactive pituitary macroadenomas cause the development of acquired secondary hypothyroidism in more than 50% of cases. The development of secondary hypothyroidism is possible years after the radiotherapy of brain tumors. As well as in case of primary hypothyroidism, the clinical manifestations of secondary hypothyroidism are non-specific. Diagnosis and management of this pathology is often complicated by its combination with the deficiency of other tropic hormones. The diagnosis of secondary hypothyroidism is based on anamnestic data and laboratory tests - the simultaneous determination of the levels of fT4 and TSH. The level of fT4 today is also used as the main marker of the adequacy of the dose of L-T4 in the treatment of secondary hypothyroidism. The results of recent studies help us to optimize replacement therapy in secondary hypothyroidism. However, the use of additional biochemical markers to assess the adequacy of replacement therapy remains unexplored.

Draft of the clinical recommendations for diagnosis and treatment of hypothyroidism

“…Вторичный гипотиреоз (ВтГ) -редкое заболевание, на его долю приходится не более 1% всех случаев гипотиреоза. ВтГ одинаково часто диагностируется как у мужчин, так и у женщин; его распространенность в популяции варьирует от 1:16 000 до 1:100 000 населения в зависимости от возраста и этиологии [4].…”

“…Для диагностики ВтГ предпочтительно исследование уровня свТ4, определение концентрации в крови общего Т4 нецелесообразно, так как зависит от концентрации ТСГ. При снижении (с возрастом, при назначении препаратов андрогенов) или увеличении (во время беременности, при приеме эстрогенов, оральных контрацептивов) уровня ТСГ будет меняться и концентрация общего Т4 соответственно [4].…”

Prevalence of Hypoteriosis Prognosis and Prevention

“…There are congenital and acquired forms of secondary hypothyroidism [3]. The prevalence of this pathology according to neonatal screening in the Netherlands is 1: 16,000, in Japan and Indiana (USA) 1: 160,000 newborns [4][5][6]. This significant difference can be explained by the fact that in Japan and the USA the screening program includes determination of TSH and T4 concentrations, while in the Netherlands the interpretation of the TSH/T4 ratio was carried out taking into account the content of thyroxine-binding globulin [5].…”